Heretofore, it has been accepted practice in the prior art to provide, for carburetors, fuel injection systems and the like, throttle valve means, carried by rotatably positionable throttle shaft means, for selectively variably controlling the rate of flow of air or motive fluid through associated induction passage means to related combustion engine means.
Usually the induction passage means, in the vicinity of the variably positionable throttle valve is, when viewed in transverse cross-section, circular. Such a circular configuration although not essential to an induction passage in, for example the vicinity of the throttle valve, is, nevertheless, the most practical and, further, does minimize the outer surface for the related available area of flow.
Generally, when viewed axially of the induction passage or bore, the throttle valve situated therein appears to be circular. However, as has been, heretofore, accepted practice, the throttle valve is, often, actually of an elliptical configuration. The adoption of an elliptical configuration as well as the degree of such elliptical configuration depends, in the main, on the angle which the throttle valve assumes with respect to the axis of the juxtaposed portion of the induction passage or bore when moved to its normal closed position, and, the amount of off-set of the throttle shaft means carrying the throttle valve.
It has been accepted practice to place the throttle shaft means in a position whereby the axis of the throttle shaft means, although contained within a plane passing normal to the axis of the induction passage or bore, is off-set some distance from but parallel to a diameter of such induction passage or bore. Consequently, the total projected area of the throttle valve generally to one side of the axis of the throttle shaft means is greater than the total projected area of the throttle valve generally to the opposite side of the axis of the throttle shaft means. The portion of the throttle valve of relatively greater area is situated in the induction passage means as to be relatively upstream of the portion of the throttle valve which is of relatively smaller effective area. This is done so that in the event the associated throttle return (closing) spring means should fail, the greater effective area of the throttle valve being disposed upstream would, because of the pressure differential thereacross and the difference in effective or projected areas of the throttle valve on opposite sides of the throttle shaft, cause the throttle valve to move toward a closed throttle condition.
In view of the foregoing, it should be apparent that, where such elliptical throttle valve configurations are employed, the distance or dimension of the throttle valve normal to the axis of the throttle shaft means (and measured to the outer-most portions therof) will be the major axis of the elliptical configuration while the distance or dimension of the throttle valve measured generally along the throttle shaft means will be the minor axis of that elliptical configuration.
Generally, in the vast majority of prior art structures, when the throttle valve is considered or referred to as being in a normally closed condition, it does not actually close all air or motive fluid flow therepast. That is, when the throttle valve is closed there is space between, generally, the periphery of the throttle and the juxtaposed surface of the induction passage which permits the flow of fluid therethrough (said space). Further, when the throttle valve is closed, such condition is referred to as idle (or idle engine operation). During relatively cold engine operation various means have been proposed by the prior art whereby when the throttle valve is closed the actual degree of closure by the throttle valve is less than the degree of closure of the throttle valve during relatively warmer or normal engine temperature operating conditions. This enables what is sometimes referred to as cold engine fast idle operation which is often necessary to sustain idle engine operation when the engine is relatively cold.
With combustion engines, of the recent past, which often had a displacement of anywhere, for example, of 300 to 460 cubic inches, slight variations, as between vehicles, in the actual space between the periphery of the throttle valve and juxtaposed surface of the induction passage, as during idle engine operation, were not of significant importance because the amount of variation was a very small percentage of the actual engine breathing rate at that time.
However, because of, among other things, governmental regultions the vehicle engines being manufactured are continually becoming smaller in displacement to where, now, an engine having a displacement of 130 cubic inches is considered to be a relatively large engine. There are now many automotive type vehicular engines which are in 1.5 liter (91.5 cubic inches) range. Many of such engines are of four cylinder configuration and, further, many of them are situated transversely of the vehicle and coupled to vehicular front wheel drive mechanisms. Of course, the vehicles employing such small engines are, themselves, small.
It should be apparent that the breathing capacity of such smaller engines (approximately 90 cubic inches) is far less than the first mentioned engines of 300 to 460 cubic inches. Therefore, if, as between vehicles employing such small engines, variations (in term of absolute area) in the actual space between the periphery of the throttle valve means and juxtaposed induction passage surface were as those experienced and easily tolerated by the relatively large engines, such variations would become intolerable because of the relatively much greater percentage of the small engine's breathing rate represented thereby.
Accordingly, it has, heretofore, become accepted practice, especially for such small engine application, to manufacture both the induction passage means and the throttle valve means to dimensions of very close (small) tolerances thereby providing for the very small opening or space (past the throttle valve means) as during closed throttle (idle) engine operation.
Even though the small engines equipped with such very accurately produced throttle-controlled induction systems initially operate in a satisfactory manner, in a relatively short time thereafter such engines may start to exhibit symptoms of general malfunction. Some of such symptoms are: (a) a possible increase in the rate of engine fuel consumption at idle; (b) an increased idle engine speed even at normal engine operating temperature; and (c) noticeable increase in resistance to throttle valve movement.
It has now been discovered that in such throttle-controlled induction passages means of such small engines which exhibited the aforestated (as well as possibly other) symptoms, a considerable degree of damage to both the surface defining the induction passage and which is generally juxtaposed to the throttle valve, and the generally peripheral surface (edge) of the throttle valve itself can exist if excessive lateral movement of the throttle shaft and throttle valve is permitted. Such damage often has the appearance of errosion. In view of such discovery, it is now concluded that the erroded-like portions actually provide, especially in terms of percentage, a much greater space for the flow of motive fluid therethrough as during idle engine operation than was originally permitted when the engine was initally provided with the high-precision-produced throttle controlled induction means and that therefore, in such engines, the idle engine speed has increased and, because of the irregularity of the juxtaposed erroded-like surface a non-uniform and increased resistance to movement of the throttle valve is often experienced.
Although it is not known for certain, it is nevertheless believed that an additional cause for the production of such eroded-like surfaces is the high degree of vibration produced by, and often inherent in, such small engines. Even if the engine is effectively vibration-isolated from the vehicle, all components, elements and accessories carried by the engine are still subjected, directly, to such engine-produced vibrations.
Accordingly, the invention as herein disclosed is primarily directed to the solution of the aforestated as well as other related and attendant problems of the prior art.